1. Technical Field
The present invention relates to an electrophotographic toner, a developer for electrophotography using the electrophotographic toner, a process cartridge and an image forming apparatus.
2. Related Art
Methods of making visible image information by forming an electrostatic latent image, such as electrophotography, have been used in various fields. In electrophotography, an electrostatic latent image is formed on a surface of a photoreceptor in a charging step and a light-exposing step, the electrostatic latent image is developed with a toner-containing electrostatic latent image developer (hereinafter sometimes referred to as “developer”), and then the image is made visible via transferring and fixing.
For the purpose of printing newspapers and direct mail, electrophotographic printing machines capable of ultra high speed on-demand printing having a linear speed higher than 1,000 mm/sec have been examined in recent years with a view to replacing an offset press. In the field of electrophotographic systems, attempts have been made to increase actual printing volume by improving compatibility with broader paper and increasing speed.
A heat roll fixing system is generally used for a thermal fixing apparatus used in the fixing; however, an offset phenomenon in which a portion of toner is transferred onto a fixing roll upon fixing may occur in this system.
Known methods for fixing a toner image after transfer including fixing a toner image by fixing a toner by pressurization and/or heating followed by solidification, fixing a toner image by fixing a toner by irradiation with light energy followed by solidification, and the like. Among these, a flash fixing method, which utilizes light and is thus free from harmful effects caused by pressurization or heating, has been the subject of much attention.
The flash fixing method has the advantages of (1) less deterioration in image resolution (reproducibility) due to smears, dust or the like generated during fixing, since pressurization of a toner for fixing of the toner is not required and thus there is no necessity for contacting (pressurizing) the toner with a fixing roller or the like, (2) there is no need to heat with a heat source or the like, so printing can be carried out immediately after power activation, without waiting until a heat source (fixing roller or the like) is preheated after power activation to a desired temperature, (3) a toner image can be fixed regardless of the material and thickness of a recording paper, such as a paper with an adhesive, a preprinted sheet or a paper having varying thickness, and (4) even if a fixing device becomes jammed by a system failure, a recording paper does not deteriorated and is not ignited by heat from a heat source.
Flash fixing is a non-contact system and makes paper delivery easy, and is thus a technique suitable for an ultra high speed printer having a processing speed in which the linear speed is higher than about 1,000 mm/sec. In an ultra high speed printer, however, significant smears occur not only on paper but also on paper-contacting members. Accordingly, there is strong demand for resistance to smears (smear resistance).